Amount Of Carbon Nanotubes Research Articles

Variable activity and selectivity for electrochemical oxidation wastewater treatment using a magnetically assembled electrode based on Ti/PbO2 and carbon nanotubes

Magnetic multi-walled carbon nanotubes (CNTs) were loaded on Ti/PbO2 electrode by a magnet in this study to improve the efficiency of electrochemical oxidation wastewater treatment (EOWT). These physically attached carbonaceous small granules worked as additional modules, giving the newly created electrode unique characteristics. Series of electrodes’ electrochemical properties, as well as their electrochemical oxidation performances against the azo dye acid red G, phenol, and real petrochemical wastewater, were studied. These carbonaceous granules improved the electrode's electroactivity as well as the affinity between the organics and the electrode. More importantly, the amount of CNTs loaded had a strong influence on the degrading efficiency and selectivity towards various target contaminants as well as their intermediate products in treating synthetic or real wastewaters. Lower CNTs loading resulted in heterogeneous electrode properties, whereas higher CNTs loading resulted in the new electrode acting as a porous carbonaceous electrode. The deeper operating mechanism of the new magnetically assembled electrode were discussed based on both the experiment results and multiphysics simulation.

Comprehensive Risk Assessment of Carbon Nanotubes Used for Agricultural Applications.

Carbon-based nanomaterials (CBNs) are often used for potential agricultural applications. Since CBNs applied to plants can easily enter plant organs and reach the human diet, the consequences of the introduction of CBNs into the food chain need to be investigated. We created a platform for a comprehensive investigation of the possible health risks of multiwalled carbon nanotubes (CNTs) accumulated in the organs of exposed tomato plants. Quantification and visualization of CNTs absorbed by plant organs were determined by microwave-induced heating (MIH) and radio frequency (RF) heating methods. Feeding mice with CNT-contaminated tomatoes showed an absence of toxicity for all assessed animal organs. The amount of CNTs accumulated inside the organs of mice fed with CNT-containing fruits was assessed by an RF heating technique and was found to be negligible. Our work provides the experimental evidence that the amount of CNTs accumulated in plant organs as a result of nanofertilization is not sufficient to induce toxicity in mice.

Carbon nanotubes/ polyacrylonitrile composite nanofiber mats for highly efficient dye adsorption

Nanofibers have unique advantages, such as high porosity and large specific surface area. Therefore, they are promising adsorption materials for the efficient removal of dyes from dyeing effluents. However, regulating adsorption properties poses significant challenges. This study incorporated different quantities of carbon nanotubes (CNT) into the polyacrylonitrile (PAN) polymer to fabricate nanofibers to address those challenges. PANnf, CNTs (3 wt%) doped PAN nanofibers (PAN3CNTnf), and CNTs (5 wt%) doped PAN nanofibers (PAN5CNTnf) were used to remove Methylene blue (MB), Malachite green (MG), and Methyl violet (MV) from different concentrations of aqueous solutions. The study examined the effect of pH, temperature, adsorbent material, and time on adsorption capacity, and applied adsorption isotherms. The maximum adsorption capacity (qm) of the dyestuff Langmuir model was 128.21 mg/g for PANnf:MB, 138.89 for PANnf:MG, 88.50 for PANnf:MV, 172.41 for PAN3CNTnf:MB, 212.77 for PAN3CNTnf:MG, 175.44 for PAN3CNTnf:MV, 158.73 for PAN5CNTnf/MB, 188.68 for PAN5CNTnf:MG, and 114.94 for PAN5CNTnf:MV. Adsorption Gibbs free energy, enthalpy, and entropy were also evaluated using adsorption isotherms at various temperatures. The negative ΔG values show that adsorption occurs spontaneously. Pseudo-first-order kinetic (PFOK) and pseudo-second-order kinetic (PSOK) models were employed to determine adsorption kinetics. The results revealed that the PSOK model agreed better with the experimental data. The experimental outcomes showed that PANnf, PAN3CNTnf, and PAN5CNTnf nanofibers were good choices for adsorbing MB, MG, and MV, which shines a light on the fabrication of multifunctional nanofiber for dye applications.

Influence of CNT Length on Dispersion, Localization, and Electrical Percolation in a Styrene-Butadiene-Based Star Block Copolymer.

This study followed the approach of dispersing and localizing carbon nanotubes (CNTs) in nanostructured domains of block copolymers (BCPs) by shortening the CNTs via ball milling. The aim was to selectively tune the electrical and mechanical properties of the resulting nanocomposites, e.g., for use as sensor materials. Multiwalled carbon nanotubes (MWCNTs) were ground into different size fractions. The MWCNT length distribution was evaluated via transmission electron microscopy and dynamic light scattering. The nanostructure of the BCPs and the glass transition temperatures of the PB-rich and PS phases were not strongly affected by the addition of CNTs up to 2 wt%. However, AFM and TEM investigations indicated a partial localization of the shortened CNTs in the soft PB-rich phase or at the interface of the PB-rich and PS phase, respectively. The stress-strain behavior of the solution-mixed composites differed little from the mechanical property profile of the neat BCP and was largely independent of CNT amount and CNT size fraction. Significant changes could only be observed for Young’s modulus and strain at break and may be attributed to CNT localization and small changes in morphology. For nanocomposites with unmilled CNTs, the electrical percolation threshold was less than 0.1 wt%. As the CNTs were shortened, the resistivity increased and the percolation threshold shifted to higher CNT contents. Composites with CNTs ground for 7.5 h and 13.5 h showed no bulk conductivity but significantly decreased surface resistivity on the bottom side of the films, which could be attributed to a sedimentation process of the grind and thereby highly compressed CNT agglomerates during evaporation.

Determination of the optimal additive content for carbon nanotube (CNT) dispersion and the influence of its incorporation on hydration and physical-mechanical performance of cementitious matrices

Carbon nanotubes (CNT) have gained great prominence due to their exceptional properties, such as high tensile strength and modulus of elasticity. However, one of the biggest difficulties regarding the use of CNT in cementitious matrices is their agglomeration tendency when added to concretes and mortars. An alternative to improve the efficiency of CNT dispersion in the matrix is the use of the dispersants (such as surfactants and additives based on polycarboxylate) with the use of an ultrasonic bath. Therefore, the aim of this work is to evaluate the effect of CNT incorporation and its influence on hydration (by means of calorimetry and X-ray diffraction) and on the physical–mechanical properties of the cementitious matrix. The results obtained pointed out that the multicriteria analysis is an efficient technique for determining the superplasticizer additive content used to disperse the CNT s and also that the presence of the properly dispersed nanoparticles accelerated the hydration of Portland cement but was not responsible for the formation of new phases. Significant differences were observed in the anhydrous and hydrated phases quantified in the cement matrix as a consequence of the amount of CNT used. It was also noted that the addition of CNT in a content equal to 0.075% led to statistically significant increases in compressive and flexural strength at 28 days of about 7% and 41%, respectively.

Carbon Nanotube Enhanced Filtration and Dewatering of Kerosene.

Current approaches to dewatering aviation fuel such as kerosene are adsorption by activated charcoal, gravity separation, etc. The objective of this work is to develop and demonstrate the filtration and dewatering of kerosene using a carbon nanotube immobilised membrane (CNIM). Highly hydrophobic membranes were prepared by immobilising carbon nanotube (CNTs) over polytetrafluoroethylene (PTFE) and polyvinylidene difluoride (PVDF) microfiltration membrane for the dewatering of ppm level water from kerosene. The effects of different CNT concentrations on membrane morphology, hydrophobicity, porosity, and permeability were characterised. After immobilising CNT into membranes, the contact angle increased by 9%, 16%, and 43% compared to unmodified 0.1 μm PTFE, 0.22 μm PTFE and 0.22 μm PVDF membranes, respectively. The CNIM showed remarkable separation efficiency for the fuel-water system. The micro/nano water droplets coalesced on the CNT surface to form larger diameters of water droplets detached from the membrane surface, leading to enhanced water rejection. In general, the water rejection increased with the amount of CNT immobilised while the effective surface porosity over pore length and flux decreased. PTFE base membrane showed better performance compared to the PVDF substrate. The CNIMs were fabricated with 0.1 and 0.22 μm PTFE at an optimised CNT loading of 3 and 6 wt.%, and the water rejection was 99.97% and 97.27%, respectively, while the kerosene fluxes were 43.22 kg/m2·h and 55.44 kg/m2·h respectively.

Melt Spinning of Elastic and Electrically Conductive Filament Yarns and their Usage as Strain Sensors

Electrically conductive fibers are required for numerous fields of application in modern textile technology. They are of particular importance in the manufacturing of smart textiles and fiber composite systems with textile-based sensor and actuator systems. Elastic and electrically conductive filaments can be used as strain sensors for monitoring the mechanical loading of critical components. In order to produce such sensorial filaments, thermoplastic polyurethane (TPU) is compounded with carbon nanotubes (CNT) and melt spun. The mechanical performances of filaments produced at different spinning speeds and containing different amounts of CNT were tested. Furthermore, the correlation between the specific electrical resistance of the filaments and the mechanical strain were analyzed depending on the CNT-content and the spinning speed.

Electrospun Carbon Nanotube-Based Scaffolds Exhibit High Conductivity and Cytocompatibility for Tissue Engineering Applications.

Carbon nanotubes (CNTs) are known for their excellent conductive properties. Here, we present two novel methods, “sandwich” (sCNT) and dual deposition (DD CNT), for incorporating CNTs into electrospun polycaprolactone (PCL) and gelatin scaffolds to increase their conductance. Based on CNT percentage, the DD CNT scaffolds contain significantly higher quantities of CNTs than the sCNT scaffolds. The inclusion of CNTs increased the electrical conductance of scaffolds from 0.0 ± 0.00 kS (non-CNT) to 0.54 ± 0.10 kS (sCNT) and 5.22 ± 0.49 kS (DD CNT) when measured parallel to CNT arrays and to 0.25 ± 0.003 kS (sCNT) and 2.85 ± 1.12 (DD CNT) when measured orthogonally to CNT arrays. The inclusion of CNTs increased fiber diameter and pore size, promoting cellular migration into the scaffolds. CNT inclusion also decreased the degradation rate and increased hydrophobicity of scaffolds. Additionally, CNT inclusion increased Young’s modulus and failure load of scaffolds, increasing their mechanical robustness. Murine fibroblasts were maintained on the scaffolds for 30 days, demonstrating high cytocompatibility. The increased conductivity and high cytocompatibility of the CNT-incorporated scaffolds make them appropriate candidates for future use in cardiac and neural tissue engineering.

Hierarchical carbon nanotubes@Ni/C foams for high-performance microwave absorption

The construction of special three-dimensional microstructure is becoming an extremely fascinating approach to upgrade the electromagnetic properties of carbon-based microwave absorption materials (MAMs) recently. Herein, we have demonstrated the successful fabrication of a series of carbon nanotubes (CNTs)@Ni/C foams (CNCFs) through two-step pyrolysis processes. It is found that the loading amount of CNTs has an obvious influence on modulating the electromagnetic diameters of CNCFs, and thus effectively tuning their microwave absorption properties. With the relative carbon content of 66.3 wt%, CNCFs-2 exhibits admirable microwave absorption performance, including the effective absorption bandwidth of 5.8 GHz with the absorber thickness of 1.8 mm and the maximum reflection loss intensity of −47.0 dB therein. Electromagnetic analysis reveals that the intrinsic attenuation ability, well-matched characteristic impedance, and multiple reflection effect synergistically work for the excellent reflection loss characteristics of CNCFs-2, which indicates rational microstructure design and appropriate chemical composition regulation are vitally important for the enhancement of microwave absorption performance. We believe these desirable microwave absorption properties can make CNCFs-2 eligible to be a very promising candidate for high-performance MAMs, and this research will provide some inspirations more or less for the development of more advanced carbon-based MAMs in the future.

Broadband microwave absorbing materials for green electronics based on poly (lactic acid)/ethylene‐vinyl acetate copolymer blends loaded with carbon nanotube

AbstractPartially bio‐based conducting polymer nanocomposites constituted by poly(lactic acid) (PLA)/ethylene‐co‐vinyl acetate (EVA) (50:50 wt%) blend loaded with different amounts of carbon nanotube (CNT) were prepared for developing microwave absorbing materials. The effect of EVA characteristics and the mixing conditions on the electrical conductivity was investigated. The higher conductivity value was achieved using PLA@CNT master batch and EVA with 28% of VA. In fact, this system presented electrical percolation threshold of 7 × 10−4 volume fraction and a conductivity value of 3 × 10−3 S/m with the addition of 0.9 wt% (0.58 vol%) of CNT. A minimum reflection loss of −29 dB (electromagnetic (EM) attenuation of around 99.9%) at 11.7 GHz and the bandwidth (<−10 dB) of 4.9 GHz was observed with the presence of 0.58 vol% of CNT, whereas RL value of around −39.4 dB (EM attenuation of around 99.99%) at 14.7 GHz and a bandwidth of 4.6 GHz was observed for the composite loaded with 0.25 vol% of CNT. Due to the outstanding microwave absorption properties and wide absorption bandwidth with low amount of CNT, these composites are promising candidates for flexible materials suitable for shielding electronic devices in a wide frequency range.

Plasma functionalization of carbon nanotubes and radical penetration mechanism

AbstractOwing to their superior properties, carbon nanotubes (CNTs) have attracted significant attention for various applications; however, their aggregation due to van der Waals forces hinders the industrial applications of CNTs. To overcome this problem, previous studies have proposed plasma functionalization, but its analysis is limited to the surface of thin‐film materials or involved small quantities of CNTs. In plasma functionalization, radicals need to penetrate from plasma into the CNTs to functionalize the entire CNTs. The radical penetration at all depths of CNTs is experimentally confirmed. The radical penetration mechanism with respect to thickness and free volume between CNTs is modeled using radical diffusion motion with the adoption of Knudsen diffusion.

Recovery of Biophenols from Olive Vegetation Waters by Carbon Nanotubes.

In this work, the possibility of using carbon nanotubes for the treatment of olive vegetation waters (OVWs) was investigated. In general, the disposal of OVWs represents an important environmental problem. The possibility of considering these waters no longer just as a problem but as a source of noble substances, thanks to the recovery of biophenols from them, was tested. In particular, predetermined quantities of olive vegetation waters were treated with carbon nanotubes. The quantities of adsorbed biophenols were studied as a function of the quantities of carbon nanotubes used and the contact time. The experimental conditions for obtaining both the highest possible quantities of biophenol and a purer adsorbate with the highest percentage of biophenols were studied. After the adsorption tests, the vegetation waters were analyzed by UV spectrophotometry to determine, in particular, the variation in the concentration of biophenols. The carbon nanotubes were weighed before and after each adsorption test. In addition, kinetic studies of the adsorption processes were considered. Carbon nanotubes proved their effectiveness in recovering biophenols.

Effect of carbon precursor flowrate on the quality and quantity of carbon nanotubes

The effect of the carbon precursor flow rate (CPFR) on the quality and quantity of CNTs is controversial. This study aimed to investigate the effect of the CPFR on the quality and quantity of CNTs at different temperatures. Our results showed that as the CPFR increased, so did the average diameter of the CNTs, indicating an improvement in the decomposition rate of acetylene at a higher CPFR. In general, the height of the CNTs also showed a peak with the CPFR. This was attributed to the competition between the decomposition rate of acetylene and the surface diffusion rate of carbon. Based on the Raman results, the graphite structures of the CNTs increased with temperature. This was ascribed to the increase in the surface diffusion rate of carbon at higher temperatures.

Structure and properties of nickel-plated CNTs/Fe-based amorphous composite coatings fabricated by high-speed laser cladding

Nickel-plated carbon nanotubes (CNTs) as additive phases can greatly improve the friction and corrosion properties of composite materials. Nickel-coated CNTs/FeCoNbBSi amorphous composite coatings were prepared on the surface of a 45-steel shaft by using high-speed laser cladding technology. Results showed that the microstructure was refined after the amount of nickel-plated CNTs increased, but the crystallization remained sever, and the amorphous content decreased from 48.36% to 27.18%. The friction coefficient decreased, and the wear morphology improved with increasing amount of nickel-coated CNTs. The friction coefficient was only 0.22 when the amount of nickel-coated CNTs was 1 wt%. In addition, the bridging behavior of the nickel-coated CNTs at the crack increased corrosion time and improved the corrosion resistance of the coating.

In Situ Growth of W2C/WS2 with Carbon-Nanotube Networks for Lithium-Ion Storage.

The combination of W2C and WS2 has emerged as a promising anode material for lithium-ion batteries. W2C possesses high conductivity but the W2C/WS2-alloy nanoflowers show unstable performance because of the lack of contact with the leaves of the nanoflower. In this study, carbon nanotubes (CNTs) were employed as conductive networks for in situ growth of W2C/WS2 alloys. The analysis of X-ray diffraction patterns and scanning/transmission electron microscopy showed that the presence of CNTs affected the growth of the alloys, encouraging the formation of a stacking layer with a lattice spacing of ~7.2 Å. Therefore, this self-adjustment in the structure facilitated the insertion/desertion of lithium ions into the active materials. The bare W2C/WS2-alloy anode showed inferior performance, with a capacity retention of ~300 mAh g−1 after 100 cycles. In contrast, the WCNT01 anode delivered a highly stable capacity of ~650 mAh g−1 after 100 cycles. The calculation based on impedance spectra suggested that the presence of CNTs improved the lithium-ion diffusion coefficient to 50 times that of bare nanoflowers. These results suggest the effectiveness of small quantities of CNTs on the in situ growth of sulfides/carbide alloys: CNTs create networks for the insertion/desertion of lithium ions and improve the cyclic performance of metal-sulfide-based lithium-ion batteries.

Improvement of thermal insulation and compressive performance of Al2O3–SiO2 aerogel by doping carbon nanotubes

Carbon nanotubes (CNTs) have attracted significant attention from researchers due to their high specific strength and good extinction properties. In this study, Al2O3–SiO2 aerogel composites doped with 0–1.0 wt% CNTs were prepared by sol-gel and supercritical drying technologies, and the effects of CNT content on their microstructure, mechanical properties, heat insulation properties, and theoretical thermal conductivity were examined. With an increase in the CNT amount, the specific surface area and pore diameter of the aerogel composites decreased, while their compressive properties were enhanced. The obtained results revealed that the 1.0 wt% CNT-doped Al2O3–SiO2 aerogel composite exhibited the best comprehensive properties, while its thermal conductivity of 0.178 W/mK at 1000 °C was 15% lower than that of pure aerogel. In addition, the theoretical thermal conductivities of all samples were calculated in the temperature range of 25–1000 °C. This study explained that the addition of CNTs can significantly improve the comprehensive properties of Al2O3–SiO2 aerogel composites.

Customizable Stretchable Transparent Electrodes Based on AgNW/CNT Hybrids via Tailoring Sizes of Building Blocks

Stretchable transparent electrodes (STEs) based on silver nanowires (AgNWs) have received considerable attention for a variety of flexible and wearable electronic/optoelectronic devices. Up to now, most efforts have focused on optimizing the STEs composed by a single AgNW conductive network. On the contrary, the structure–performance correlations of STEs formed by a hybrid percolative network which comprises the AgNW and a second conductive nanomaterial have rarely been discussed. In this work, we fabricated hybrid-type STEs by selecting three kinds of carbon nanotubes (CNTs) with different diameters to pair with three types of AgNWs with variable length-to-diameter ratios. The size effect of building blocks of the nine combinations on the optical, electrical, and mechanical properties of resultant STEs was thoroughly investigated. The results reveal that AgNWs and CNTs with smaller diameters are beneficial to achieve hybrid electrodes with a high transmittance and low haze. AgNWs with larger length-to-diameter ratios contribute hybrid STEs with lower sheet resistance by adding a suitable amount of CNTs. Importantly, the smaller differences in diameters of AgNWs and CNTs lead to more effective capillary-force-induced welding, which boosts both the conductivity and stretchability of STEs. An optimized AgNW/CNT hybrid electrode demonstrated a transmittance of 66.4% and a haze of 11.0% at a sheet resistance of 8.70 Ω sq.–1 which could endure a uniaxial tensile strain as large as 490%, while its resistance increased only 46.9% after experiencing 1000 cycles of 50% tensile strain. Alternating current electroluminescent devices based on such AgNW/CNT hybrid STEs were also successfully developed, showing uniform and stable patterned luminescence.

Nanostructured thermoelectric composites for efficient energy harvesting in infrastructure construction applications

Although numerous investigations have been performed on thermoelectric (TE) fields, no notable studies have been conducted on TE structural materials. In this study, the electrical characteristics of cement were induced by incorporating carbon nanotubes (CNTs). Although cement can serve as a TE material owing to its low thermal conductivity, its extremely low electrical conductivity hinders its feasible application. The introduction of cement composites containing small amounts of CNTs is suggested as a solution. CNTs can improve the TE performance of cement-based composites because they exhibit superior electrical conductivity and are suitable as additives for carbon isotope-based composites. Such composite materials can be used as TE structural materials for energy harvesting in buildings. Therefore, to analyze the feasibility of the cement/CNT composites, the electrical conductivity, Seebeck coefficient, and thermal conductivity were measured by varying the CNT concentration using 4-probe measurement and ASTM D5470 methods. The electrical conductivity was improved by approximately 104 times as the CNT concentration increased from 0.0625 to 0.25 wt% while maintaining a relatively stable Seebeck coefficient, whereas the thermal conductivity remained in the insulating material region. The results showed that the critical CNT concentration associated with the percolation threshold was relatively low (∼0.1 wt%). This study may contribute to the development of self-powered sensor systems in buildings based on structural temperature differences.

High-speed identification of suspended carbon nanotubes using Raman spectroscopy and deep learning

The identification of nanomaterials with the properties required for energy-efficient electronic systems is usually a tedious human task. A workflow to rapidly localize and characterize nanomaterials at the various stages of their integration into large-scale fabrication processes is essential for quality control and, ultimately, their industrial adoption. In this work, we develop a high-throughput approach to rapidly identify suspended carbon nanotubes (CNTs) by using high-speed Raman imaging and deep learning analysis. Even for Raman spectra with extremely low signal-to-noise ratios (SNRs) of 0.9, we achieve a classification accuracy that exceeds 90%, while it reaches 98% for an SNR of 2.2. By applying a threshold on the output of the softmax layer of an optimized convolutional neural network (CNN), we further increase the accuracy of the classification. Moreover, we propose an optimized Raman scanning strategy to minimize the acquisition time while simultaneously identifying the position, amount, and metallicity of CNTs on each sample. Our approach can readily be extended to other types of nanomaterials and has the potential to be integrated into a production line to monitor the quality and properties of nanomaterials during fabrication.

Deformation and fracture behaviour of alumina-zirconia multi-material nanocomposites reinforced with graphene and carbon nanotubes

An effort to improve the low fracture toughness of monolithic alumina (Al2O3) ceramic demands microstructural manipulation with nanostructured materials such as zirconia (ZrO2), Graphene (GN) and Carbon Nanotubes (CNTs). Despite these attempts, the fundamental understanding of the mechanical properties and deformation behaviour of multiple combinations of these second-phase additives within the advanced Al2O3 structure are still being explored. In this respect, Al2O3-based nanocomposites reinforced with optimum amounts of ZrO2(10 wt%), GN(0.5 wt%) and CNTs(2 wt%) were evaluated via hot-pressing at 1600 °C, preceding colloidal mixing of the Al2O3 matrix and nanostructured additives. Mechanical properties such as fracture toughness (KIC) and bending strength (σf) measured using three-point bending techniques including single edge notched beam (SENB) test, and direct crack measurement (DCM) methods were calculated from the near-dense fabricated multi-material nanocomposites and benchmarked against the monolithic Al2O3 material under similar experimental conditions. From the conventional SENB test, the fracture toughness values increased by up to 60% on the addition of only 10 wt%ZrO2 to the monolithic Al2O3, whilst a drastic increase by up to 159% was achieved with the incorporation of both GN and CNTs within the Al2O3–ZrO2 structure, as compared to the monolithic Al2O3. The KIC values obtained from SENB tests were typically lower than the DCM method, but similar trend in the toughness behaviour were realized regardless. Bending strength of the prepared monolithic Al2O3 was also increased by up to 46% with the combined additions of ZrO2, GN and CNTs. Toughening and strengthening mechanisms including pull-outs by GN and CNTs, crack arrest and cack bridging were identified as the main source of enhancement in the mechanical properties of the multi-material nanocomposites. The addition of carbon additives also influenced monoclinic and tetragonal ZrO2 phase transformations, which also contributed to the overall mechanical behaviour of the Al2O3-10 wt%ZrO2 nanocomposites.